Geological History

1. What is the correct chronological sequence of the following ‘periods’

What is the correct chronological sequence of the following ‘periods’ in the Earth’s geological timescale?

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  • 1. Cambrian
  • 2. Carboniferous
  • 3. Cretaceous
  • 4. Devonian

Select the correct answer using the code given below.

1-4-2-3
1-2-4-3
1-2-3-4
2-1-3-4
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UPSC CBI DSP LDCE – 2023
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The correct option is A.
The geological timescale periods mentioned belong to the Phanerozoic Eon. Their correct chronological order from oldest to youngest is:
1. **Cambrian** (Paleozoic Era, starting ~541 million years ago)
2. **Devonian** (Paleozoic Era, ~419 – 359 million years ago)
3. **Carboniferous** (Paleozoic Era, ~359 – 299 million years ago)
4. **Cretaceous** (Mesozoic Era, ~145 – 66 million years ago)
The Paleozoic Era follows the Precambrian and precedes the Mesozoic Era. The order of periods within the Paleozoic is Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian. The Mesozoic Era consists of the Triassic, Jurassic, and Cretaceous periods.

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2. Which one of the following geologic time periods is associated with th

Which one of the following geologic time periods is associated with the first appearance of the marsupials?

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Lower Cretaceous
Upper Cretaceous
Early Jurassic
Middle Jurassic
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The first appearance of marsupials in the fossil record is associated with the Upper Cretaceous geologic time period.
– Marsupials (Metatheria) and placental mammals (Eutheria) are thought to have diverged from a common ancestor during the Cretaceous period.
– The earliest definitive marsupial fossils date back to the Upper Cretaceous, specifically from North America and Asia.
The Cretaceous period spans from approximately 145 to 66 million years ago. It is divided into the Lower Cretaceous (145-100.5 million years ago) and the Upper Cretaceous (100.5-66 million years ago). Mammals, including early marsupials and placentals, diversified significantly during the Cretaceous, particularly after the extinction of the dinosaurs at the end of the period. Earlier mammal forms existed in the Jurassic, but the divergence and appearance of distinct marsupial lineage fossils occurred later.

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3. Which one of the following is the oldest era in Geological History det

Which one of the following is the oldest era in Geological History determining the age of various rock types ?

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Precambrian
Mesozoic
Cenozoic
Paleozoic
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In the geological timescale, the largest division is the Eon. The history of the Earth is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic. The first three eons together are often informally referred to as the Precambrian Supereon, preceding the Phanerozoic. The Phanerozoic Eon is divided into three eras: Paleozoic, Mesozoic, and Cenozoic. The Precambrian represents the vast majority of Earth’s history, from its formation about 4.5 billion years ago until the beginning of the Paleozoic era about 541 million years ago. Therefore, the Precambrian is the oldest era (or supereon encompassing the oldest eras) listed.
The Precambrian Supereon, comprising the Hadean, Archean, and Proterozoic Eons, represents the oldest and longest interval in Earth’s geological history, preceding the Phanerozoic Eon and its subdivisions (Paleozoic, Mesozoic, Cenozoic Eras).
The Paleozoic Era saw the “Cambrian explosion” of life, the Mesozoic is known as the age of dinosaurs, and the Cenozoic is the current era, known as the age of mammals. These are all significantly younger than the Precambrian.

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4. In terms of geological time scale, the quaternary period consists of t

In terms of geological time scale, the quaternary period consists of two epochs. They are :

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Pleistocene and Pliocene
Holocene and Pleistocene
Pleistocene and Miocene
Holocene and Eocene
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The correct option is B.
The Quaternary period, the most recent geological period in the Cenozoic Era, is divided into two epochs: the Pleistocene and the Holocene.
The Pleistocene epoch is characterized by repeated glaciation events and the evolution of modern humans. The Holocene epoch is the current epoch, beginning after the last glacial period ended, approximately 11,700 years ago, and is characterized by the rise of human civilization.

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5. The Indian desert also known as Marusthali is believed to be under the

The Indian desert also known as Marusthali is believed to be under the sea during which one of the following eras ?

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Cenozoic era
Palaeozoic era
Mesozoic era
Archaean and Pre-Cambrian era
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UPSC CDS-2 – 2022
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The correct answer is C) Mesozoic era.
Geological evidence, including the presence of marine fossils (like ammonites) found in areas like Jaisalmer within the Thar Desert, suggests that parts of the region were submerged under a shallow sea during the Mesozoic era, particularly during the Jurassic and Cretaceous periods. This indicates that the area was part of the Tethys Sea or its remnants before tectonic uplift and regression of the sea formed the landmass.
The Cenozoic era followed the Mesozoic and is the “Age of Mammals,” characterized by the formation of the Himalayas and the development of the modern Indian landscape. The Palaeozoic era preceded the Mesozoic and saw the formation of ancient mountain ranges and significant life evolution. The Archaean and Pre-Cambrian eras represent the Earth’s earliest history, long before the formation of such features. The marine transgression evidence in the Thar Desert points specifically to the Mesozoic.

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